Gel-lifted fingerprints tested for drugs in forensics breakthrough

Forensic gel allows fingerprints to be viewed against a clear background, improving visualisation of the print. It has long been assumed that the gel carrier may also contain traces of other forensic material such as drugs or even DNA. However, existing techniques have not been able to distinguish between the chemicals in the gel and additional chemicals that could be forensic evidence.

Testing for the presence of the sleeping pill Zolpidem, the Loughborough team employed a technique called sfPESI-MS that used a rapid separation mechanism to distinguish the drug substance from the background of the gel.

The process involves sampling the chemicals from the gel lifters into tiny liquid droplets. Chemicals extracted into the droplets are then ionized, with drug substance chemicals more surface active than the gel chemicals, enabling them to be separated from the mixture. The presence of particular drugs can then be confirmed using mass spectrometry. The research is published in the journal Drug Testing and Analysis.

“This is the first time that analysis of gel-lifted prints for a drug substance has been accomplished and shows that lifted prints and other forensic marks can be interrogated for useful information,” said research lead Dr Jim Reynolds, from Loughborough’s Centre for Analytical Science.

“Since gel-lifted prints and marks can be stored for many years, the technique could be of real use in cold cases where additional information may prove useful to either link or exonerate a suspect to the investigation. Working with police forces and applying the method to cold case samples could help bring criminals to justice who may have thought they have got away with it.”

Reynolds and study co-author Dr Ayoung Kim tested the technique using Zolpidem-laced fingerprints lifted from glass, metal, and paper surfaces in a laboratory setting. They now hope to work with police forces to analyse stored gel-lifted prints and use the method to identify other substances.

 “Zolpidem was the focus of our research, but the method could just as easily be applied to other drug substances a person may have been handling and could be applied to other chemicals such as explosives, gunshot residues, paints, and dyes,” said Dr Reynolds.

“By linking chemical information to the fingerprint, we can identify the individual and link to the handling of an illicit substance which may prove useful in a prosecution.”